Finally, studies using peripheral blood mononuclear cells (PBMC) from human subjects have found reduced levels of the “open” chromatin mark, acetylated histone 3, in schizophrenia patients compared to nonpsychiatric controls or bipolar subjects [10, 11], increased levels of the “closed” chromatin mark H3K9me2 compared to controls [12], and a reduced ability to alter chromatin structure using HDAC inhibitors both as clinically administered [13] as well as in culture [10, 12]. This evidence concerns the gene HDAC9 and schizophrenia.